196 On Dimorphism of Arsenic, Antimony and Zinc. 
memoirs in vol. vi, of the Memoirs of the American Academy of 
Arts and Sciences. It is sufficient for the present purpose to 
state that the composition of the crystals was in every case 
sensibly the same as that of the alloy. : 
is investigation seems to prove that zinc is capable of assum- 
ing a monometric condition and thus of crystallizing in connec- 
tion with copper in the same way that sulphate of copper may 
be made to crystallize in connection with sulphate of iron, taking 
the form of green vitriol although it generally assumes the form 
: 
history of the subject 
uring the course of some experiments on the compounds of 
uct 
with carbonate soda was determined in the usual way. The 
result gave 
Zine, : - - - - - - - 81°18 
Arsenic, PCa ele eel er Lop egg 
100°00 
ments. ‘The presence of a certain amount of impurity seems to 
favor metallic crystallization and it is possible that it may be the 
* + . * . . if 
works near Clausthal in the Harz, are familiar to mineralogists, 
and the author has found that a small quantity of lead on the 
other hand greatly facilitates the crystallization“of antimony. 
Similar facts have been noticed in.the ease of bismuth so that dis- 
tinct crystallization instead of being the test of purity in the 
case of a metal is quite the reverse. ‘'o what extent the presence 
of these impurities may effect the crystalline form of the metal 
